Telephone-exchange system



Dec. 29, 1925.

L. PoLlNKowsKY TELEPHONE EXCHANGE SYSTEM Filed Nov. 17, 1922 5 Sheets-Sheet l mvenfor: L/pa Po/inko Wsk y.

' Aify.

Dec. 29 1925.

Lu. POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed Nav. 17, 922 5 Sheets-Sheet 2 /r7 vemfor: L/pa Po/inko vvsk y.

Dec. 29, 1925. 1,567,295

L. POLINKOWSKY TELEPHONE EXCHANGE SYSTEM Filed Nov. 17, 19 2 5 Sheets-Sheet 3 I /n venfor: L/pa Pa/inkawsky Dec. 29 1925- L. POLINKOWSKY TELEPHONE EXCHANGE SYSTEM 5 Sheets-Sheet Filed NOV. 17 1922 /n ven/an L/pa Pa/in/ro ws/(y Any Dec. 29, 1925. 1,567,295

L. POLlNKOWSKY I TELEPHONE EXCHANGE SYSTEM Filed Nov. 17. 19 5 Sheets-Sheet 5 Q l\ Q E 9 by M w/42734 Patented Dec. 29, 1925.

uurrau srATEs PATENT OFFICE.

LIPA POLINKOWSKY, 0F ANTWERP, BELGIUM, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed November 17, 1922. Serial No. 601,473.

To all whom it may come-m.

Be it known that I, LEPA loL'iNKowsKY, a citizen of Russia, residing at 14 Rue de Bastion, Antwerp, Belgium, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to systems in which connections areestallished in part by automatic switching apparatufand in part by operators.

The object of the invention is a system wherein an improved supervisory and controlling arrangement is provided at a connecting operators position. i

A feature of the invention relates to a supervisory signal, normally serving to advise the operator that the called party has withdrawn from the connection, which also serves when a second call is extended over the same circuit to notify the operator thereof.

A further feature relates to a time meastiring device which operates to restore the indicating mechanism at the operators position in case the calling party abandons the call prematurely. I

These and other advantages contemplated by this invention will become more clearly understood from the following description and appended claims.

Referring to the drawing, Figs. 1 to 5 inclusive, when placed one below the other in order, illustrate a telephone exchange sys' tem embodying the features of this invention.

Fig. 1 shows a calling subscribers line terminating in a full mechanical otiice, diagrammatically illustrated, and also a trunk line outgoing from the mechanical office and terminating a call indicator operators position in a manual otiice. This figure also shows a called subscribefis line terminating in the manual otiice.

shows-a pair of cord tinder switches connections with the various the operatofis position.

Fig. 3 illustrates the control circuits of a call indicator, which is associable through the cord finder switches with the various cord circuits.

Fig. l discloses the register switches of the call indicator.

Fig. 5 illustrates the number lamps.

According to the system disclosed here in, calling lines in the mechanical o'llice, are associated, due to the initiation of a call, with a central otlice register sender 121 upon which the record of the wanted line is established. Thereafter the register sender exercises control over any desired number of selective switches, one of which, switch 111, is diagrammaticallyshown on the drawing. F or outgoing calls to the manual otlice equipped with call indicators, the switch 111 under the control of the register sender 121 selects a trunk such as trunk 101, 102 leading to the distant office and terminating in cord circuit 130.

Following the extension of the line to the manual ofiice, impulses are transmitted overthe extended connection under the control of the sender 121 to determine the setting of the operators call indicator for displaying the number of the wanted line upon the number lamps.

.Inasmuch as the invention relates only to the features of the equipment in the manual office and due to the well known character of the apparatus located in the machine switching otlice for accomplishing the purpose outlined, the latter has only been shown in diagrammatic form. For a full disclosure of a system wherein call indicators are controlled from the register sender in a mechanical ofl'ice, reference is made to the patent to Polinkowsky, No. 1,395,595 issued November 1, 1921.

The cord tinder switches 200 and 201 are of the ordinary step-hy'step rotary type and comprise a stepping magnet and a plurality of brushes and cooperating terminal rows. Each of these switches has access to a given number of cords and is set in motion automatically whenever a call appears on find the same. The cord finder in finding the calling trunk or operators cord thereby associates the same with the call indicator.

The switch 330 is also a rotary step-bystep switch, the purpose of which is to control the sequence of operations during the setting of the indicator registers. The switch 340 is a switch of the same type and is used as a time measurement device The registers 400, 405, 415 on which the numerical digits are recorded are also rotary step-by-step switches. The switch 400 comprises a stepping magnet 401 and the brushes 407, 408, 409 and 411. The switch 405 comprises the stepping magnet 402 and the brushes 412, 413, 414 and 416. Switch 410 consists of the stepping magnet 404 and the brushes 417 to 420 inclusive. Similarly, the register switch 415 comprises the magnet 406 and the brushes 421 to 424 inclusive.

It is believed that a more thorough understanding of the invention may be had from a detailed description of the operation involved in the establishment of a connection. Assume for this purpose that the subscriber of line 110 in the mechanical office wishes to obtain connection with the subscriber of line 112 which is located in a distant manual oflice. The subscriber of line 110 on ini tiating the call causes the extension of his line over the usual line finder or line switch and the association of an idle sender 121 by means of a sender selector switch 119, 120. The subscriber sets up the number on the register sender 121 by transmitting impulses over the line and following this, the requisite number of switches including the switch 111 are positioned to select an idle trunk 101, 102 outgoing to the distant called manual office.

Immediately that the connection is extended to the operators cord circuit 130, a fundamental circuit is completed from battery through the resistance 113, inner lower contact of relay 155, inner upper contact of relay 118, conductor 102, over the trunk line to the distant oflice through the usual stepping relay of the sender 121 and returning over conductor 101 through to the uppermost contact of relay 118 both windings of relay 103 in series, coil 114, to ground at the upper back contact of relay 155. Relay 103 operates and closes a circuit from battery through the winding of relay 104, inner left contact of relay 105 to ground at the contact of relay 103. Relay 104 closes a circuit from ground through the resistance 107, inner right contact of relay 104, conductor 115, inner left back contact of relay 106, lamp 123 to battery. Due to the resistance 107, the lamp 123 glows dimly to advise the operator that an incoming cell is being received at her position.

Relay 104 also closes a circuit from ground through its inner left contact, conductor 116, outer left normal contact of relay 106, winding of relay 152 to battery. Relay 104 furthermore closes a circuit from ground through its inner left contact, conductor 117, winding of relay 217 to battery. Relay 217 operates and closes a circuit for the stepping magnet 202 of the trunk finder switch 200. This circuit may be traced from battery through the winding and contact of magnet 202, right contact of relay 217, outer right contact of relay 220, to ground at the back contact of relay 221. The magnet 202 interrupts its own circuit and steps the brushes 203, 204, 205 from position to position to search for the calling cord circuit 130. When the trunk finder 200 finds the calling cord, a circuit is closed from battery through the windings of relay 118 outer left contact of relay 104, conductor 124, terminal 226, brush 205, conductor 227, outermost left contact of relay 343 thence through the left winding of relay 221, outer left contact of relay 217 to ground at the inner left contact of relay 220. The test relay 221 energizes in this circuit and locks in a circuit through its right hand winding and front contact to ground. During the operation of the trunk finder switch, the circuit through the magnet 202 also extends over a branch through the winding of relay 219. So long as relay 221 is inert, however, relay 219 remains inactive. When relay 221 becomes operated as described, it removes the shunt and relay 219 operates in series with the stepping magnet 202. The resistance of relay 219 is such that the stepping magnet 202 fails to operate and the brushes of the finder switch, therefore, come to rest 011 the terminals representing the calling cord circuit 130.

The relay 118 also energizes in series with relay 221 and in so doing, opens the circuit of relay 103. Relay 103 releases and severs the circuit of relay 104. Before relay 104 releases, relay 118 locks in a circuit from battery through its windings and lowermost contact, lowermost contact of relay 155, and thence over conductor 124 to ground at the contact of relay 221 as traced. Relay 104 in releasing, opens the original circuit of relay 118 and also opens the circuit of relay 152. Relay'152, however, is now looked over a substitute circuit traceable from battery through the winding of said relay, outermost left back contact of relay 106 to ground at the inner lower cont-act of relay 118.

Then relay 104 becomes deenergized, it opens the circuit of relay 217 which in turn, releases and opens the circuit of the stepping magnet 202 of the cord finder switch 200. Other cord finder switches similar to the switch .200 having access to the same group of cord circuits may also be operating simultaneously under the control of circuits similar to those already described. As soon as the cord finder switch 200 locates the calling cord and relay 217 becomes released, the operating circuits of all of the hunting cord finders are opened.

The relay 219 in operating in series with the magnet 202 closes the following circuit: battery through the winding of relay 221, lowermost contact of relay 21.), winding of relay 219 to ground. Hence, when the relay 217 release; to open the circuit of magnet 202, the relay 219. remains energized in series with relay 22%, and the latter relay also operates. The calling supervisory lamp 123 i now lighted dimly in a circuit traceable from battery through said lamp, inner left contact of relay 106, conductor 115, brush 206, right contact of relay 224-, outer left back contact of relay 302, resistance 305 to ground.

Relay 219 also closes a circuit from ground through its uppermost front contact, winding of relay 220 to battery. Re lay 220 closes a circuit from ground through its inner right front contact, conductor 229, contacts of stepping magnets 106, 101, 402 and 101 in series, conductor 127, back contact of relay 301, outer right contact of relay 303, inner right contact of relay 302, winding of slow-to-release relay 300 to battery. Relay 300 energizes and closes a circuit for relay 301. Relay 301 operates and establishes a fundamental circuit over which the registers of the call iinlicator are positioned from the distantiuechanical office. The fundamental cir cult may be traced from battery through the windings of relays 301 and 3110, re

sistance 332, outer right contact of relay 3011, outer left back contact of relay 311, conductor 32?, middle lower contact of relay 219, brush 1, conductor 230, thence over the trunk to the mechanical ollice through the us'ual stepping relay in the sender 121 and returning over the trunk to conductor 231, brush 203, inner lower contact of relay 219, conductor 328, to ground at the inner left contact of relay 311. Provided the fundamental circuit is closed at the sender 121, relays 1 and 310 operate and modify the fundamental circuit to the extent that it now leads from battery through the windings of relays 30a and 310, resistance 332, contact of relay 310, and thence to ground as above traced independently of relay 301.

Relay an in operating opens the circuit of relay 300. Before relay 300 has time to rele :e and open the circuit of relay 301, a cncuit is closed from battery through winding of relay 312, left front contact of relay 301.. front contact of relay 301i, corn ductor 12?, contacts of magnets 101, 102, 101 and 10:; in series. conductor 22!), to ground. at the inner right front coniact of relay 220. Relay 312 which is also slow-torelease operates and closes a circuit from ground through its outer right contact, left normal contact of relay 321, welding of the stepping magnet 320 of the control switch 330 to battery. The magnet 32.) energizes preparatory to the advancing of the brushes when the magnet becomes dccncrgized. After an interval, relay 300 releases and opens the circuit of relay 301. Relay 801 in turn, opens the circuit of relay 312. After a further interval, relay 312 dccnm'gizes, opens the circuit of magnet -320 and the control switch 330 moves to its first position terminals.

As soon as the relays 301 and 312 become dccnergized, a circuit is completed from battery through. the winding of relay 321, left contact of relay 312, left back contact of relay 301, front contact of relay 301, thence over conductor 42? to ground as hereinbefore traced. Relay 326 completes a circuit from ground through its right con tact, conductor 333, brush 22 1, (position 1) conductor 53-1, winding of stepping magnet -1l0l of the thousands register to battery. gnet 1-01. operates mcparatory to releas ing the brushes into their next position upon (leez'i pgizcition. Relay 320, moreover, conipletes a circuit from ground through its left contact, Contact of relay 310. resistance 332, windings of relays 310 and relay 30lto battery. Relay 020 at its left contact thus completes a holding circuit for the relays 30st and 310 in shunt of the winding of the stepping relay (not shown) in the other end of the .lundznncnlal circuit. namely. at the register scndcr 121 in the distant ol'licc. Relays 310 and 304: remain energized while the stepping rela v releases to record one impulse on a set of counting relays or similar well known device. lihen the stepping magnet -l-0l has completely energized. it opens its contact and sevcrs the circuit of relay Relay 320 releases and opens the circuit of magnet 401. which in turn deenergizes and advances the brushes of the register one step. Relay 320 also removes the shunt from the fundamental circuit and the stepping relay at the sender is again energized.

Immediately that magnet 101 fully rcleases, relay 320 energizes and the same performance takes place a second time. This procedure continues until the register sender 121 determines that a sutlicient number of impulses have been sent to represent the thousands digit, at which time itsevere the fundamental circuit permitting the release of relays 304 and 310.

lVith relay 30 relcascd. lhc above traccd circuit is completed for relay 300 which in turn causes the operation of relay 301. When the fundamental circuit is again closed at the distant oflice, relays 304 and 310 operate and the circuit of relay 300 is opened. Before relay 301 becomes energized, however, a circuit is closed from battery through the winding of relay 312, left front contact of relay 301, front contact of relay 304 and thence to ground as traced over conductor 427. Relay 312 operates and closes the circuit of stepping n'iagnet 320. After relay 301 releases, it opens the circuit of relay 312 which in turn causes the control switch 330 to be moved into its second position. \Vith the fundamental circuit closed and relays 312 and. 301 released, the above traced circuit is closed for relay 326. Relay 326 closes a circuit from ground through its right contact, conductor 333, brush 324, (position 2) conductor 338, winding of stepping magnet 402, to battery. Relay 326 also, at its left contact, closes a holding circuit for relays 304 and 310 in shunt of the stepping relay in the fundamental circuit. Magnet 402 energizes to prepare the brushes of the register 405 and also opens the circuit of relay 326. Relay 326 releases and opens the circuit of magnet 402. hilagnet 406 steps the brushes forward one step. Belay in releasing, also removes the shunt from the fundamental circuit and the sender 121 records the transmission of an impulse. This action continues, the register 405 stepping from position to position until the sender 121 is satisfied at which time the fundamental circuit is opened and relays 304 and 310 release. Relay 304 prevents further operation of relay 326 and also closes the above traced circuit for relay 300. In the manner described, relay 301 energizes causing the operation of relay 312 causing in turn the energizing of the stepping magnet 320 of the control switch 330. When the fundamental circuit is again closed and relays 304 and 310 operate relay 312 deenergizes to cause the control switch to be moved into its third position.

After an interval, relay 301 becomesreleased and the circuit of relay 326 is again established. Relay 326 completes a circuit from ground through its right contact, conductor 333,-brush 324, (position conductor 343, winding of the tens register stepping magnet 404, to battery. Magnet 404 energizes and prepares the brushes of the tens register 410 for advancement. Relay 326 on its left cont-act also places a shunt on the fundamental circuit. Magnet 404 on complete energization, opens the circuit of relay 326 and this relay releases to in turn open the energizing circuit of magnet 404 and also to remove the shunt from the fundamental circuit. In this manner, the brushes of the register 404 are moved from position to po sition until the fundamental circuit is opened by the register sender 121. The relays 304 and 310 release upon the opening of the fundamental circuit and in so doing 4 cause the closure of the circuit already traced for the relay 300. Relay 300 operates causing relay 301 to energize. lVhen the fundamental circuit is again closed, relay 304 operates and relay 312 is energized to close a circuit for magnet 320. After an interval, relay 301 releases, opening the circuit of relay 312 which in turn releases to open the circuit of magnet 320 and the brushes of the control switch 330 move to their fourth position terminals.

Nith relays 312 and 301 released and the fundamental circuit closed for the transmission of the units digit, the circuit hereinbefore traced for relay 326 is completed. Relay 326 completes a circuit from ground through its right contact, conductor 333, brush 324, (position 4) conductor 344, Winding of the stepping magnet 406 to battery. Magnet 406 operates and at its contact opens the circuit of relay 326. Relay 326 in operating, also places the shunt around the stepping relay into the fundamental circuit. Relay 326 on having its circuit opened by the magnet 406 releases and opens the energizing circuit of said stepping magnet and also removes the shunt from the fundamental circuit. The brushes of the register 415 are moved forward one step. This action continues until the sender 121 is satisfied at which time the fundamental circuit opened and relays 304 and 310 become deenergized. Relay 304 closes the circuit of relay 300 which in turn, closes the circuit of relay 301. These relays, however, are not effective to advance the control switch 330 at this time.

A circuit may now be traced from battery through the winding of relay 311, conductor 339, brush 422, conductor 345, outer right contact of relay 303, back contact of relay 304 thence over conductor 427 as traced to ground. Relay 311 operates and bridges the winding of relay 335 across the tip and ring conductors of the circuit leading back to the mechanical oflice. Relay 311 completes a cir- 1 cuit from battery, resistance 371, inner right contact of relay 311, winding of relay 302 to ground. Relay 302 does not operate since it is shunted by a direct path to ground at the back contact of relay 336.

When the apparatus at the mechanical oflice is placed in condition for conversation, talking battery is supplied through windings of a repeating coil or similar de vice in a well known manner through the tip and ring conductors leading to the operators cord circuit in the manual office. The relay 335 operates in this circuit and closes a circuit from battery through the resistance 337, outer left contact of relay 303, right hand high resistance winding of relay 336, right contact of relay 335, inner left contact of relay 224, brush 207, conductor 233 to ground at the lower back contact of relay 140. Relay 336 closes a locking circuit for itself fro-m battery through the resistance 337, outer left contact of relay 303, left hand low resistance winding of relay 336, front contact of relay 336 to ground. The low resistance of the left hand winding of relay 336 so reduces the potentional applied to the right hand winding of other similar relays 336 that none of these latter relays can operate to associate the indicator lamps with other corresponding registers. hen

relay 336 operates, it opens the shunt around the winding 302 and this latter relay actuates Relay 302 completes a circuit from ground through its inner left contact, winding of relay 341 to battery. Relay 341 at its contacts closes circuits for the number lamps shown in Fig. 5.

Assume for example, that the thousands, hundreds, tens and units digits of the wanted number are such that the. register 400 is set on its number 3 position terminals, register 405 on its number 5 position terminals, register 410 on its number 4 position termina-ls and register 415 on its number 3 position terminals. A circuit is thereupon closed from battery through the thousands lamp 500, conductor 501, terminal 430, brush 411, terminal 431, brush 413, outer right contact of relay 425, conductor 432, outer left contact of relay 341 to groimd. Another circuit is closed from battery through the lamp 502, conductor 503, terminal 433, brush 416, terminal 434, brush 423, conductor 435, inner right contact of relay 301, out-er right cont-act of relay 341 to ground. Still another circuit is completed from battery through the lamp 504, conductor 505, terminal 436, brush 420, conductor 437, outer left contact of relay 341 to ground. Lastly a circuit is completed from battery through the lamp 506, conductor 507, terminal 438, brush 424, conductor 439, to ground at the outer right contacts of relay 341. These lamps are illuminated to display the number of the wanted subscribers line.

lVhen relay 302 operates, it closes a circuit from battery through the lamp 123, inner left back contact of relay 1063, conductor 115, brush 206, right contact of relay 224, outer left front contact of: relay 302, winding of relay 350 to ground. The resistance of relay 350 is such that the lamp 123 does not illuminate in series therewith. Relay 350 energize-s and closes the circuit for the relay 351. Relay 351 operates and closes a circuit for the lamp 123 in shunt of relay 350. The lamp 123 glows brightly and relay 350 which is slow-to-release commences to retract its armature. 1Vhen relay 3550 releases, it opens the circuit of relay which also releases its armatures slowly. By means of the relays and 351, the lamp 123 is intern'iittently illuminated and extinguished. This signal notifies the operator that the call has been displayed on her number lamps and is awaiting attention.

The operator reads the number displayed on the lamps and seizing the plug 125 of the cord 130 inserts it in the jack of the called line 112. A circuit is now closed from battery through the winding of relay 140, ring of plug 125, ring of the jack, wincL ing of relay 141, to ground. Relay 140 operates and closes a circuit from ground through its lower front contact, winding of relay 106 to battery. Relay 106 operates and a circuit is closed from battery through the calling lamp 123, inner left front contact, of relay 106 to ground at the outer right contact of relay 105. Another circuit is closed from battery through the called supervisory lamp 122, inner right front contact of relay 106, to ground at the right contact of relay 150. The lamp 122 illuminates indicating that the called subscriber has not responded. Relay 106 closes a. locking circuit for relay 152 traceable from battery through the winding and left front contact of relay 152, outer left front contact of relay 106, to ground at the inner lower contact of relay 118. Relay 106 also closes a circuit from battery through the winding of relay 151, outer right contact of relay 152, to ground at the right back contact of relay 153. Relay 151 operates and closes a circuit from battery through its winding and inner lower contact, winding of relay 153, to ground at the left back contact of relay 154. Relay 153 does not operate since its winding is shunted by the original energizing circuit I for relay 151.

Relay 151 completes a circuit from ground through its lower contact, winding of relay 105, winding of relay 155 to battery. Re-

lay 155 operates and opens the circuit of relay 118. Relay 118 closes the tip and ring conductors 101 and 102 through the windings of relay 103. Provided the calling end of the circuit has not been released, the relay 103 is operated in series with the usual battery supplied at the mechanical oliice and closes a holding circuit for relays 155 and 105 as follows: battery through the Winding of these latter relays, inner left front contact of relay 105 to ground at the contact of relay 103. Relay 113 in releasing. opens the holding circuit of relay 152 and this relay becomes deenergized to open the original energizing circuit of relay 151. Relay 151 is now held energized in series with relay 153 and this latter relay also operates. Relay 153 closes a circuit from battery through the coil of thermostat 15'? to ground at the rightfront contact of relay 153. After an interral, thermostat- 157 curls and closes its contact. A circuit is now completed from battery, resistance 159, winding of relay 160, left contact of relay 153, contact of thermostat 157 to ground at the right front contact of relay 153. Relay 160 operates and closes a circuit from the source of ringing current 126 through the left front contact of said relay, uppermost front contact of relay 151, upper front contact of relay 140, thence over the tip side of the calledsubscribers line 112 through the substation bell and returning over the ring side of the line to ground through the winding of relay 141. Vhile ringing current is thus being applied, a circuit is closed from battery through the coil of thermostat 158, contact of thermostat 157 to ground at the right front contact of relay 153. After a sufficient interval, the thermostat 158 curls its element and a circuit is established as follows: battery through the winding of relay 154, resistance 161, contacts of thermostats 158 and 157 to ground at the right front contact of relay 153. Relay 154 operates and closes a circuit in shunt of the winding of relay 160. Relay 160 having its winding shunted, releases its armatures and opens its outer right contact. The opening of this contact opens the circuit of relays 153 and 151 which relays become deenergized, disconnecting the ringing cur-- rent from the called line. After the thermostats have released, the relay 154 becomes deenergized.

If the subscriber does not respond to the first application of ringing current, the operator may withdraw the plug 125 causing the release of relays 140 and 106. Relay 106 completes a circuit from battery through the winding of relay 152, inner right contact of relay 105, inner right back contact of relay 106, to ground at the right contact of relay 150. Relay 152 operates and when plug 125 is reinserted in the jack relays 140 and 106 again operate. The relay 160 opcrates in the manner already described and ringing current is again applied.

7 When the called subscriber answers, a circuit is completed from battery through the winding of relay 150, uppermost back contact of relay 151, upper front contact of relay 140 thence over the tip side of the line through the loop of the substation, returning over the ring side of the line through the winding of relay 141, to ground. Relay 150 operates and opens the circuit of lamp 122 advising the operator that the called subscriber has responded. The calling supervisory lamp 123 is also extinguished at this time due to the energization of relay 105.

WVhen relay 155 operates, it opens the cir cuit of the test relay 221. Relay 221 becomes deenergizedand short-circuits relay 219. Relay 219 releases and a circuit is closed from battery throughthe windings of relays 321 and 343 in parallel, right normal contact of relay 321-, left back contact of rep lay 342, conductor 352, uppermost back contact of relay 325, uppermost back contact of relay 219, conductor 240, brush 325, to ground. Relays 321 and 323 operate and look through the right front contact of relay 321, brush 325 to ground. Relay 343 closes a circuit from battery through the winding of relay 303, right contact of relay 303, brush 325 to ground. Relay 303 opens the circuit of relay 336 and this relay releases to remove the busy potential from the right hand windings of other similar relays whereby the indicator lamps may be taken for use in connection with other registers. Relay 336 at its left back contact shunts the relay 302 and this latter relay releases and opens the circuit of relay 341. Relay 341 becomes deenergized and opens the circuits of the illuminated lamps.

Relay 321 also closes the circuit from battery through the winding of magnet 320, left front contact of relay 321, contact of magnet 320, brush 322, (position 4) to ground. The magnet320 operates, interrupts its own circuit and moves the control switch to its fifth position. A circuit is now completed from battery through the winding of magnet 401, conductor 334, brush 324, (position 5), conductor 333, innermost left contact of relay 343, brush 323 (position 5), conductor 347, brush 407, contacts of magnets 401, 402, 404 and 406 in series, conductor 229, inner right front contact of relay 220 to ground. It will be noted that the re lay 220 following the release of relay 217 is held energized in a circuit over conductor 240 to ground through the brush 325. The magnet 01 operates and interrupts its own circuit to advance the brushes of the register 400 from position to position. When the register reaches its normal position, the brush 407 encounters the terminal 440, the stepping circuit of the magnet 401 is opened and a circuit is established as follows: battery through the winding of magnet 320, left front contact of relay 321, contact of magnet 320, brush 322, (position 5) conductor 353, terminal 440, brush 407 thence through the contacts of magnets 401, 402, 404 and 406 to ground as above traced. The stepping magnet 320 of the control switch operates in this circuit and advances the brushes to their sixth position terminals.

A circuit is now completed from battery through the winding of magnet 402, conductor 338, brush 324 (position 6), inner left contact of relay 343, brush 323, (position 6'),

conductor 348, brush 412, contacts of mag nets 402, 404, 406, and thence to ground as above traced. The register 405 is advanced to its normal position at which time a circuit is closed from battery to the winding of magnet 320, left front contact of relay 321, contact of magnet 320, brush 322 (position 6) conductor 349, brush 412, contacts of magnets 402, 404, 406 and thence to ground as traced. Magnet- 320 operates and ad vances the control switch into position 7.

In this position, the control switch circu t is completed from battery through the winding of the tens register magnet 404, conductor 343, brush 324, (position 7) conductor 333, inner left contact of relay 343, brush 323, (position 7) conductor 354, brush 417, contacts of magnets 404, 406, conductor 229, to ground. Magnet 404 operates and restores the tens register to its normal position at which time a. circuit is closed as above traced through the winding of the magnet 320 to the brush (position 7) thence by way of conductor 355, brush 417, contacts of magnet 404, and 408 to ground over conductor 229. Magnet 320 operates and steps the control switch in the position 8.

In a similar manner, a circuit is completed from battery through the winding 0t magnet 406, conductor 344, thence through the brush 324 to brush 323 as traced, thence over the eighth position terminal of brush 323, conductor 356, brush 421, contact of magnet 406 to ground over conductor hen the unit-sregister 415 is advanced to its normal position, a circuit similar to the ones traced is completed for magnet 320 and the control switch 330 moves into position 9. A circuit is nowclosed from battery through the winding of magnet 320, left front contact of relay 321, contact of magnet 321, brush 322 to ground. The magnet 320 interrupts its own circuit and moves from its ninth position into position 10 and then into position 11. On reaching position 11, the brush 325 encounters the non-grounded terminal indicating the normal position 01" the switch and the holding circuits of relays 321, 343 and 220 are opened. Relay 321 opens the circuit of magnet 320 and the control switch comes to rest.

When the conversation finished, the calling and called subscribers replace their receivers on the switchhooks. The calling subscriber opens the circuit of relay 103. Relay 103 releases and opens the holding circuit of relays 105 and 155. A circuit is now completed from battery through the lamp 123, inner left front contact of relay 106 to ground at the outer right contact of relay 1.05. The lamp 123 burns and notifies the operator that the calling subscriber has hung up his receiver.

The called subscriber in releasing opens the circuit of relay 150. The relay 150 closes a circuit from ground through its right contact. inner right front contact of relay 100, lamp 122 to battery. The lamp 122 illuminates to advise the operator that the called subscriber has hung up his receiver. The operator thereupon withdraws the plug 125 from the ack permitting the release of relay 140. Relay 140 opens the circuit of relay 103 and the lamps 123 and 122 are extinguished.

It may happen that the called subscriber fails to replace his receiver on the. switchhook after conversation is finished. Assume for example, that following conversation, the calling subscriber hangs up his receiver and the outgoing end of the trunk is re leased in the mechanical oflice but the *alled subscriber fails to replacehis receiver .and the operator neglects to remove the plug 125 from the jack. A ssume also that while this condition prevails, the trunk is again seized at the mechanical office. As already eX- plained, the seizure of the trunk causes the operation of relay 103 in the cord circuit. Relay 103 causes the operation of relay 104 which initiates the operation of a cord finder switch. The cord finder finds the calling cord, and connects to call indicator thereto and the record is registered on the indicator in the manner already described. However, as will be presently described, the number lamps are not illuminated under a condition of this character.

Since the operator has failed to withdraw the plug from the jack and since the called subscribers receiver is oli' the switchhook, relays 140 and 150 are operated. When relay 104 actuates, it closes a circuit from ground through its inner left contact, conductor 116, outer left front contact of relay 100, left back cont-act of relay 152, inner left front contact of relay 106, lamp 122 to battery. The supervisory lamp 122, which normally serves to advise the operator that the called subscriber has hung up his receiver, illuminates in this circuit to notify the operator that a second call has been received on that particular cord. The operator in response to this signal withdraws the plug 12:) of the jack of the previously called line. Relay 100 releases and opens the circuit of lamp 122, and also closes the previously traced circuit for illuminating the lamp 123 dimly.

Nhile a plug 125 remains in the jack oi. the first called line, and relay 140 is energized, the circuit of the test relay 3% is held open. Immediately that the operator removes the plug, however. relay 330 operates as described provided the relay 335 is energized, and in so doing removes the shunt from around the winding of relay 302. Relay 302 causes the operation oi relay 341 which closes the circuit for the selected number lamps to display the number of the second called line. The operator reads this number and thereupon inserts the plug 125 in the jack of the corresponding line.

A time device 340 shown in Fig. 3 is employed for the purpose oi bringing about a release of the call indicator registers in case the calling subscriber abandons the call prior to the time the number has been displayed llll) on the indicator lamps. As soon as the units register has been positioned, it will be recalled the relay 311 is energized in a circuit already traced. Relay 311 closes a circuit from ground through the brush 325, conductor 358, inner left contact of relay 303, left contact of relay 335, outer right contact of relay 302, winding of right normal contact of relay 342, outer right contact of relay 311, conductor 359, brush 363, (position 1) right contact of stepping magnet 363, winding of relay 360 to battery. Relays 342 and 360 operate in this circuit and the relay 342 locks in a circuit from battery through its right front contact and winding and thence to ground as traced through the brush 325. Relay 360 in operating, closes a circuit from battery through its winding, contact of magnet 362, contact of relay 360, resistance 366, winding or relay 361 to ground. Relay 361 is slow-to-operate and requires an appreciable interval for attracting its armature. When relay 351 finally operates, it closes at its front contact, a circuit for magnet 362. Magnet 362 operates and opens the circuit of relay 360 and relay 361. Relay 361 releases and opens the circuit of magnet 362 and the brushes 363, 364, 365, etc., are advanced one step. The circuit is now closed from battery through the winding of relay 360. contact of magnet 362, brush 363, resistance 367 to ground. Relay 360 operates and closes a circuit for relay 361 which in turn causes the operation of magnet 362 to step the brushes forward another position. This procedure continues, the time measure switch 340 moving from position to position to count time following the bridge of relay 335 across the contact. If a call progresses regularly, the relay 335 will operate as hereinbefore explained before the time measure switch 340 becomes affected. However, if the subscriber at the mechanical office abandons the call, relay 335 remains inert, and when the time measuring switch reaches a given posi tion, it closes a circuit from ground, brush 365, terminal 368, thence through the left front contact of relay 342, windings of relays 321 and 343 in parallel to battery. These relays operate and bring about the restoration of the indicator equipment in the manner already explained.

In case a predetermined number of calls are received at an operators position, simultaneously, it is desirable to prevent the further extension of calls thereto until those i already existing have been handled. Relay 218 is included in series with the resistance 171 by the relay 104, but does not operate. lVhen, however, two relays 104 for example, are energized simultaneously, one in connection with each of two different calls, the parallel circuits through the winding of relay 218 affords sufiicient current to operate said relay. Relay'218 in operating opens the circuit which normally extends from ground through the manual switch 235, back contact of relay 218, inner upper contact of relay 22. inner upper contact of relay 219, winding of relay 216 to battery. Relay 216 releases and removes ground from the conductor 236 leading back to the mechanicaloflice. Relay 174 in the mechanical office thereupon becomes deenergized and opens the circuit of relay 176. Relay 176 opens the energizing circuit of relay 177 whereupon a condition is placed upon the test terminal 127 of the outgoing trunk shown and also a similar condition is placed upon the test terminals of all other trunks outgoing to the same mechanical office for rendering them non-selective.

If it is desirable to give the manual operator information regarding the thousands designation of the wanted line, this may also be done. The trunks such as 101, 102 outgoing from the mechanical office are associated in the selector switch 111, in groups and each group will have a digit designation as usual. The appearance of these trunks at the manual office in the bank of the cord finder switches 200 may likewise be appointed to correspond with the grouping of the same trunks in the terminal bank of the selector switch 111. that the trunk 101, 102 belongs in a group, the thousands designation of which is represented by the lamp 509, the cord finder 200 on locating the trunk 101, 102 comes to rest when brush 208 engages the terminal 238 and when relay 341 operates, the following circuit is closed: battery through the lamp 509, conductor 510, inner right back contact of relay 425, conductor 441, terminal 238, brush 208, outer right contact of relay 224, to ground at the inner left contact of relay- 341.

What is claimed is:

1. In a telephone system, subscribers lines, a trunk for making connections with said lines, an automatic selective switch for extending a connection over said trunk, a supervisory signal operated in response to the replacement of his receiver by the called subscriber, and means for operating said signal in response to the extension of a second connection over the, trunk before such trunk is disassociated from the first called line.

2. In a telephone system, subscribers lines, a trunk for making connections with said lines, an automatic selective switch for extending connections over said trunk, a super visory signal individual to said trunk and operative in response to the replacement of his receiver by the called subscriber, and means efiective to operate said signal if the trunk is appropriated for making a connection to a second called line before it has been disassociated from the previously called line.

Assume for example, C

3. In a telephone system, subscribers lines, an operators position, a trunk leading to the operators position serving to extend connections to said lines, selective switches for extending connections over said trunk, an indicating mechanism atthe operators position for designating called lines, means controlled over the trunk when appropriated for a connection for setting said mechanism, a supervisory lamp for normally advising the operator when the called party replaces his receiver, said indicating mechanism being arranged to take a second setting over the trunk if such trunk is appropriated for a second connection before it is fully disassociated from a previously called line, and means for operating said supervisory lamp when the trunk is appropriated for a second connection before being disassociated from the previously called line.

at. In a telephone system, subscribers lines, an operators position having cord circuits for extending connections to said lines, switches for extending calls to said cords, a

mechanism for indicating to the operator the designations 0f called lines, a signal operative when the called subscriber replaces his receiver, and means for operating said signal when a second call is extended to a cord not yet released from a previously called line t9 notify the ope 'ator that the indicating mechanism is waiting to display the number of the second called line.

5. In a telephone system, an operators position having an indicating mechanism thereat, means for extending connections to the operators position, means for setting the indicating mechanism to display the number of a wanted line, and a time measuring device effective when an extended connection is released to cause the restoration of said indicating device to normal.

6. In a telephone system, an operators position having an indicating device thereat comprising registers and number lamps, means for extending connections to the op erators position, means for setting said registers, means for selecting and illuminating said lamps in accordance with the settings of the registers to display awanted designation, means for restoring the registers to normal after the designation has been displayed, and a time measuring device effective when a connection is abandoned before the display of the designation for restoring the said registers to normal.

In witness whereof, I hereunto subscribe my name this 2nd day of November A. D.,

LIPA POLINKOWSKY. 

